This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Impact of hypertonic-hyperoncotic saline solutions on ischemia-reperfusion injury in pedicled flaps in rats, as measured by Modulated Imaging tissue spectroscopy. Tissue transfer flaps are a method of moving any tissue from a donor area of the body to a recipient site. The reconstructive surgeon employs two major types of tissue transfer flaps, the pedicled tissue transfer flap and the free tissue transfer flap. A pedicle flap consists of soft tissues connected to the donor location only by the artery and vein, which provide the blood supply to the pedicled tissue transfer flap. The tissues of the pedicled flap are moved from the donor site to the recipient site by rotating the soft tissue of the flap on the arteries and veins, thereby allowing the transfer of tissue from one location to another on the body. In a free tissue transfer flap the arteries and veins are divided from the donor site, and re-attached to the recipient site using microsurgical techniques. Improved surgical techniques have resulted in a high percentage of successful tissue transfer flaps for tissue defects after trauma or oncological ablative surgery. However, flap failures still occur and are usually caused by global insufficiency of blood supply secondary to mechanical obstruction of the vessels, systemic disease, or the ischemia-reperfusion (I/R) injury. This I/R injury occurs directly after reestablishment of the blood flow to ischemic tissues, this process occurs to some extent with all free tissue transfer flaps as the flap is transiently ischemic during the period between detachment from the donor site and re-attachment at the recipient site. I/R injury can also occur with pedicle flaps as well if the blood supply to the flap is interrupted due to "kinking" or external compression of the arteries and / or veins to the flap. Severe I/R injury can result in vascular damage within the tissue transfer flap, leading to poor blood flow and further ischemia, which can result in partial or complete flap loss. Partial or complete flap loss can be devastating to patients undergoing reconstructive surgery. Hypertonic-hyperoncotic saline (HHS) solutions are solutions that contain high concentrations of salts. Prior clinical and animal studies have found that the administration of HHS solutions at the time of re-establishment of blood flow to ischemic tissue can lessen the extent and severity of I/R injury. The goal of this specific research project is to test the impact of HHS solutions on the I/R injury after re-establishment of blood flow to an ischemic tissue transfer flap. We hypothesize that these solutions are able to minimize the effects of I/R injury after the restoration of blood flow to ischemic tissues and thus increase overall flap survival. We believe from our prior experiments and results using hypertonic saline in a rat free flap model that this is the case. This experiment attempts to measure the improved microvascular blood flow by using Modulated Imaging (MI) Spectroscopy. We plan to do so by using MI spectroscopy to demonstrate the changes in total, oxygenated, and deoxygenated hemoglobin as well as the changes in water content within an ischemic flap after reperfusion when treated with hypertonic saline.